For many products it is important to have a good understand of how change in physical properties can cause processes and delivery from a product to fail.
For inhalation products this is especially important as generally very small (high surface area to volume ratio) particles need to be delivered. These small particles need to be very well characterized in terms of bulk and surface properties in order to produce a good and reproducible product.
Batch-to-batch variability can be seen for reasons such as amorphous content that is produced during high energy milling, and which gradually changes and recrystallizes over time. The study of this effect is one of Graham’s research themes.
General help is available in the design and understanding of data to assist in the formulation, especially of more at risk formulations such as inhalation product.